The present disclosure relates to a negative electrode active material, a battery, a battery pack, an electronic apparatus, an electric vehicle, an electrical storage apparatus and an electricity system.
Recently, greater capacity and faster charging-discharging speed of lithium-ion secondary batteries are strongly demanded. For a purpose of realizing greater capacity than that with the use of a carbon material, the uses of Si (silicon) and the like for negative electrode active materials have been studied. However, so far, it may have a problem using Si and the like, in terms of cycle characteristics and rapid charge-discharge.
In view of such circumstances, techniques of modifying material properties of a commercially available Si active material with easy processing have been studied.
For example, a technique of modifying Si material properties by surface-coating of the Si is under study. It is reported that alumina, and SiO, are effective in improving cycle characteristics. SiO coating is likely to be especially effective, but regarding SiO coating, because of instability of SiO, it seems that so far there is no good method other than vapor phase coating by using CVD (Chemical Vapor Deposition) and the like. However, the cost to install equipment for this method would be large, and in addition, it is not easy to fully-coat the surface of a Si particle since the method is a vapor phase method. Meanwhile, for example, Japanese Patent Application Laid-open No. 2007-305424 suggests a technique of adding a different element to a Si material.